The modern internal combustion engine incorporates chain guides and chain tensioners in relation to valvetrain or balanceshaft chain drive systems. Such chains replace, for example, gears and timing belts that connect the crankshaft with the camshafts. While providing superior performance and durability when compared with earlier approaches to linking the crankshaft and the camshafts, timing chains must operate under a predetermined amount of tension to minimize wear and to reduce both vibration and noise.
To answer this need, a timing chain is placed under tension over its entire travel by one or more chain tensioners. Chain tensioning arms commonly provided in internal combustion engines respond to longitudinal stretching of the chain and control longitudinal and transverse vibrations of the chain, which may be caused by excitations arising from the camshaft, the crankshaft and associated components. Chain guides are used in conjunction with the chain tensioning arms to maintain the proper course of chain travel.
According to known technology, chain tensioning arms and chain guides are composed of any of a variety of metals, typically cast metals. While proving generally satisfactory, because of metal-on-metal friction today's metal chain tensioning arms and guides are sometimes known to wear prematurely and to generate an undesirable level of engine noise. In fact, chain drive systems have relatively higher friction than belt or gear drive systems.
In response to this problem, various plastics have been proposed for use as materials for chain tensioning arms and guides. However, while solving the problem of engine noise caused by known metal tensioners and guides, the plastic versions of these components still suffer from poor wear characteristics.
As in so many areas of vehicle technology there is always room for improvements related to the design of timing chain tensioning arms and guides as used in the internal combustion engine.